JP2010245387A - Wavelength variable laser, wavelength variable laser device, and wavelength variable laser control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate wavelength control by shifting a peak wavelength without changing a peak wavelength interval. <P>SOLUTION: A wavelength variable laser 100 includes a DFB portion 2 including a first optical waveguide 10a including a diffraction grating forming region 10d as a region having a first diffraction grating 31 formed thereon and a gain region 10e positioned so as to continue in a waveguide direction to the diffraction grating forming region 10d, a DBR portion 3 including a second optical waveguide path 10b provided with a second diffraction grating 32a and optically coupled to the first optical waveguide 10a, a DFB portion wavelength control electrode 45 provided at a position for injecting a DFB portion wavelength control current in the diffraction grating forming region 10d in the first optical waveguide 10a of the DFB portion 2, and an electrode 41 for gain provided at a position for injecting a gain current larger than the DFB portion waveguide length control current in the gain region 10e in the first optical waveguide 10a of the DFB portion 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wavelength tunable laser, a wavelength tunable laser apparatus, and a wavelength tunable laser control method.

  Conventionally, as a wavelength tunable laser, for example, Patent Document 1 proposes a DR-type wavelength tunable laser using a distributed reflector (DR) type tunable laser and using SG (Sampled Grating) as a diffraction grating. ing. In this DR type wavelength tunable laser, a DFB region having a gain region and a phase control region, and a diffraction grating having a sampling period different from that of the DFB region forms SG. A DBR region.

  In the wavelength tunable laser described in Patent Document 1, the wavelength of each reflection peak is selected using the Vernier effect by controlling the injection current to the phase control region and DBR region of the DFB region.

JP 2004-336002 A

  However, in the laser described in Patent Document 1, since the diffraction grating is provided in the gain region of the DFB region, if the peak wavelength of the reflection spectrum is shifted, the peak wavelength interval changes and the wavelength control is complicated. There was a problem of becoming.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention has an object to provide a wavelength tunable laser and a wavelength tunable laser control method that makes wavelength control easy by shifting the peak wavelength without changing the peak wavelength interval as much as possible. To do.

  In order to solve the above-described problem, a wavelength tunable laser according to the present invention includes a diffraction grating formation region in which a first diffraction grating is provided, a gain region that is located continuously in the diffraction grating formation region and the optical waveguide direction, A DFB portion including a first optical waveguide including a DBR portion including a second optical waveguide provided with a second diffraction grating and optically coupled to the first optical waveguide; A DFB part wavelength control electrode provided at a position where a DFB part wavelength control current is injected into a diffraction grating formation region in one optical waveguide, and a gain larger than the DFB part wavelength control current in a gain region in the first optical waveguide of the DFB part. And a gain electrode provided at a position where a working current is injected.

  In this configuration, the first optical waveguide includes a continuous diffraction grating formation region and a gain region, the first diffraction grating is provided in the diffraction grating formation region, and a diffraction grating is provided in the gain region that generates gain. Therefore, the peak wavelength is shifted without changing the peak wavelength interval, and the effect that wavelength control becomes easy can be obtained.

  The wavelength tunable laser preferably further includes a phase shift unit that is provided between the DFB unit and the DBR unit and shifts the phase of the light guided through the first optical waveguide and the second optical waveguide. It is. With this configuration, it is possible to obtain an effect that laser oscillation occurs due to a low threshold current.

  The second diffraction grating is preferably formed of SG. With this configuration, since the phase shift at each reflection peak of SG is small, phase control can be simplified.

  Further, it is preferable that the second diffraction grating forms an SSG (superstructure grating). With this configuration, since the reflectance is high, a larger light output can be obtained.

  In order to solve the above-described problems, a wavelength tunable laser device according to the present invention includes a reflection spectrum of the wavelength tunable laser and a first optical waveguide provided with a first diffraction grating by adjusting a DFB wavelength control current. A DFB unit wavelength control unit that controls one peak wavelength of a plurality of peak wavelengths to a predetermined value, and a second diffraction grating provided by adjusting a DBR unit wavelength control current injected into the DBR unit. A DBR unit wavelength control unit configured to control one peak wavelength among the plurality of peak wavelengths of the reflection spectrum in the two optical waveguides to a predetermined value.

  With this configuration, it is possible to more appropriately control the reflection spectrum in the first optical waveguide and the reflection spectrum in the second optical waveguide to desired values.

  The wavelength tunable laser device includes an optical output monitor unit that monitors the optical output of light oscillated by the wavelength tunable laser, and phase control that is injected into the phase shift unit so that the optical output monitored by the optical output monitor unit is maximized. It is preferable to further include a phase control current control unit that controls the current. With this configuration, a larger light output can be obtained.

  In order to solve the above-described problem, the wavelength tunable laser control method of the present invention adjusts the DFB wavelength control current in the wavelength tunable laser to adjust the first optical waveguide provided with the first diffraction grating of the wavelength tunable laser. By adjusting the DFB unit wavelength control step for controlling one peak wavelength of the plurality of peak wavelengths of the reflection spectrum in the waveguide to a predetermined value and the DBR unit wavelength control current in the wavelength tunable laser, And a DBR section wavelength control step for controlling one peak wavelength of the plurality of peak wavelengths of the reflection spectrum in the second optical waveguide provided with the diffraction grating to a predetermined value.

  With this configuration, the reflection spectrum in the first optical waveguide is controlled by injecting current into the diffraction grating formation region of the first optical waveguide, and further, the current injected into the second optical waveguide is controlled. Thus, the reflection spectrum in the second optical waveguide is controlled. Thereby, it becomes possible to obtain an effect that the wavelength control becomes easier.

  The wavelength tunable laser control method includes a light output monitoring step for monitoring the light output of light oscillated by the wavelength tunable laser, and the DFB of the wavelength tunable laser so that the light output monitored in the light output monitoring step is maximized. It is preferable to further include a phase control current control step for controlling a phase control current that is provided between the unit and the DBR unit and that is injected into the phase shift unit that shifts the phase of light.

  By adjusting the current injected into the phase shift unit, a larger light output can be obtained.

  According to the present invention, it is possible to provide a wavelength tunable laser and a wavelength tunable laser control method that facilitate wavelength control by shifting the peak wavelength without changing the peak wavelength interval.

It is a figure which shows the wavelength tunable laser apparatus in 1st Embodiment. It is a figure for demonstrating the function of the control part and monitor part which are shown in FIG. It is a figure which shows the flow of a process of the wavelength variable laser control method which concerns on embodiment. It is a figure which shows the wavelength tunable laser apparatus in 2nd Embodiment. It is a figure which shows the wavelength tunable laser apparatus in 3rd Embodiment.

<First Embodiment>
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate descriptions are omitted.

  FIG. 1 shows a configuration of a wavelength tunable laser device 1a in the present embodiment. As shown in this figure, the wavelength tunable laser device 1a of this embodiment includes a wavelength tunable laser 100, a control unit 200 that controls electrodes and the like disposed at appropriate positions of the wavelength tunable laser 100, and And a monitor unit 300 that outputs a monitoring result to the control unit 200. The oscillation wavelength variable range of the wavelength tunable laser 100 in this embodiment is 1.25 to 1.75 micrometers, and can be used as a wavelength-multiplexed light source for optical communication. However, there is no intention to limit the oscillation wavelength of the wavelength tunable laser 1a.

  The wavelength tunable laser 100 includes a DFB unit 2, a DBR unit 3, and a phase shift unit 4 positioned between the DFB unit 2 and the DBR unit 3.

  The DFB unit 2 including a function for generating a gain includes a first optical waveguide 10 a provided with a first diffraction grating 31. The first diffraction grating 31 in the DFB portion 2 forms an SG having a unit structure (segment) (hereinafter referred to as “DFB unit structure”) having a length in the waveguide direction of Λs. The DFB unit structure includes a portion where the first diffraction grating 31 is provided and a portion where the first diffraction grating 31 is not provided.

  The first optical waveguide 10a is located in a portion where the first diffraction grating 31 is provided, the diffraction grating formation region 10d, and the diffraction grating formation region 10d, which is continuously located in the optical waveguide direction. The gain region 10e is a portion where the diffraction grating 31 is not provided. In the present embodiment, the diffraction grating formation region 10d and the gain region 10e in the first optical waveguide 10a are composed of a single (same) layer and have the same composition.

  The DBR unit 3 includes a second optical waveguide 10b provided with a second diffraction grating 32a that forms an SSG. The second diffraction grating 32a forms an SSG composed of a unit structure (segment) (hereinafter referred to as “DBR unit structure”) whose length in the optical waveguide direction is Λr. This DBR unit structure is a chirped diffraction grating having a wavelength tunable range as a diffraction wavelength. The diffraction wavelength of this chirped diffraction grating is discretized. That is, the DBR part 3 has a superstructure diffraction grating SSG composed of a plurality of DBR part unit structures.

  The light oscillated by the wavelength tunable laser 100 according to the present embodiment has a vernier effect (using a slight difference in the peak wavelength interval of the reflection spectrum in the first optical waveguide 10a and the second optical waveguide 10b). The effect can be controlled to a desired wavelength.

  Therefore, the optical path length of the DFB unit unit structure in the DFB unit 2 is different from the optical path length of the DBR unit unit structure in the DBR unit 3.

The period of the first diffraction grating 31 is preferably between the minimum period (Λ ₂ ) and the maximum period (Λ ₁ ) of the second diffraction grating 32a. In addition, by dividing Λ ₁ to Λ ₂ discretely and changing the diffraction wavelength in steps, the problem that the formation of the chirped diffraction grating cannot change the diffraction grating period continuously can be solved. . Λs is preferably between 25 micrometers and 250 micrometers. Of the length of Λs, the length in which the first diffraction grating 31 is provided is preferably 5 to 50 percent of the total length of Λs. The entire length of the DFB portion 2 is preferably 200 micrometers to 600 micrometers.

  Between the DFB unit 2 and the DBR unit 3, a phase shift unit 4 for shifting the phase of light guided through the optical waveguide 10 is formed. The phase shift unit 4 has a function of controlling the optical path length of the optical waveguide 10 so that laser oscillation occurs with a low threshold current.

The first optical waveguide 10a, the second optical waveguide 10b, and the third optical waveguide 10c are optically coupled (hereinafter, the first optical waveguide 10a, the second optical waveguide 10b, and the third optical waveguide 10c). The entire optical waveguide 10c is referred to as the optical waveguide 10). The coupling coefficient of the diffraction grating of the DFB portion 2 and the DBR portion 3 is 50cm ^-1 ~500cm ^-1.

  The optical waveguide 10 includes a core layer 12 sandwiched between optical confinement layers 11 and 13. In FIG. 1, the first diffraction grating 31 and the second diffraction grating 32a are described as being provided in the optical confinement layer 13 (below the core layer 12 in FIG. 1). There is no intention to limit the portion to be provided to the optical confinement layer 13. The first diffraction grating 31 and the second diffraction grating 32a may be provided in the light confinement layer 11 (that is, above the core layer 12 in FIG. 1). The optical confinement layers 11 and 13 can be made of a GaInAsP-based material or an AlGaInAs-based material having a band gap energy larger than that of the core layer 12.

  A light emitting end face 60b that is a surface from which the laser light L1 is emitted in the DFB section 2 and a light emitting end face 60b that is provided on the DBR section 3 and from which the monitor light L2 for monitoring light (described later) is emitted. Has a low reflection coating with a dielectric multilayer film.

  Among the core layers 12, the core layer 12 forming the phase shift unit 4 and the DBR unit 3 has a GaInAsP system having a band gap energy larger than that of the active layer forming the DFB unit 2 or It is preferable to use an AlGaInAs-based material.

  In the SSG formed by the second diffraction grating 32a, a plurality of DBR unit structures composed of chirped diffraction gratings are formed. The length of the second optical waveguide 10b in the optical waveguide direction is preferably 300 to 900 micrometers. In addition, Λr is preferably from 25 micrometers to 250 micrometers.

Period of chirped grating of the second diffraction grating 32a, the wavelength variable range from .lambda.1 .lambda.2 of the tunable laser 100 (λ1 <λ2), when the group refractive index as n _e, a range of lambda ₁ of lambda ₂ . Here, Λ ₁ and Λ ₂ satisfy Equation 1 and Equation 2.

In the actual formation of the chirped diffraction grating, since the period of the diffraction grating cannot be changed continuously, Λ1 to Λ2 are discretely divided to change the diffraction wavelength in steps. As described above, when the period of the diffraction grating of the first diffraction grating 31 is Λ 0, it is preferable that Expression 3 is satisfied.

  The wavelength tunable laser 100 of the present embodiment emits light at a desired wavelength by using the vernier effect of the peak wavelength of the reflection spectrum in the first optical waveguide 10a and the peak wavelength of the reflection spectrum in the second optical waveguide 10b. It is oscillating.

The coupling coefficient of the diffraction gratings of the DFB part 2 and the DBR part 3 is 50 cm ⁻¹ to 1000 cm ⁻¹ .

  The optical waveguide 10a that generates a gain in the DFB portion 2 can have, for example, a GaInAsP-based or AlGaInAs-based multiple quantum well structure.

  The DFB part wavelength control electrode 45 is located above the DFB part 2 and at a position where a current (hereinafter referred to as “DFB part wavelength control current”) is injected into the diffraction grating forming region 10 d provided with the first diffraction grating 31. Is provided. Further, a gain electrode 41 is provided at a position where an electric current (hereinafter referred to as “gain current”) is injected into the gain region 10 e above the DFB portion 2. The density of the DFB wavelength control current is smaller than the threshold current density of the diffraction grating formation region 10d. That is, no gain occurs in the diffraction grating formation region 10d. However, an appropriate current is injected to reduce the light absorption of the diffraction grating formation region 10d.

  A phase control electrode 42 for injecting a phase control current, which is a current for controlling the phase of light guided through the optical waveguide 10, into the phase shift unit 4 is provided above the phase shift unit 4.

  Above the DBR unit 3, a DBR unit that injects into the DBR unit 3 a current that adjusts the reflection spectrum by changing the refractive index of the second optical waveguide 10 b (hereinafter referred to as “DBR unit wavelength control current”). A wavelength control electrode 43 is provided.

  A second cladding layer 23 is provided above the optical waveguide 10, and a contact layer 21 is further provided above the second cladding layer 23. The contact layer 21 can be made of highly doped n-type GaInAs.

  A first cladding layer 22 is provided below the optical waveguide 10, and a semiconductor substrate 24 is provided below the first cladding layer 22. An n-type electrode 44 is provided below the semiconductor substrate 24. When an n-type semiconductor substrate is used, the first cladding layer 22 can use n-type InP, and the second cladding layer 23 can use p-type InP.

  The control unit 200 has a function of controlling the gain electrode 41, the phase control electrode 42, the DBR unit wavelength control electrode 43, and the DFB unit wavelength control electrode 45.

  FIG. 2 is a diagram illustrating a functional configuration of the control unit 200 and the monitor unit 300. The control unit 200 includes a DFB unit wavelength control unit 101, a DBR unit wavelength control unit 102, a phase control current control unit 103, a light output control unit 104, a memory 105, and a determination unit 106.

  The DFB unit wavelength control unit 101 adjusts the DFB unit wavelength control current to adjust one peak wavelength among the plurality of peak wavelengths of the reflection spectrum in the first optical waveguide 10a provided with the first diffraction grating 31. Is controlled to λ0 which is a desired oscillation wavelength.

  The DBR unit wavelength control unit 102 adjusts the DBR unit wavelength control current by using the DBR unit wavelength control electrode 43, so that a plurality of reflection spectra of the second optical waveguide 10b in which the second diffraction grating 32a is provided are reflected. A function of controlling one of the peak wavelengths to λ0 is provided.

  The phase control current control unit 103 has a function of controlling a phase control current that is a current for changing the phase of light guided through the optical waveguide 10 using the phase control electrode 42. For example, the control method may be such that the optical output of the laser light oscillated by the wavelength tunable laser 100 is maximized.

  The optical output control unit 104 has a function of controlling the optical output of the wavelength tunable laser 100 to a desired value by adjusting the gain current using the gain electrode 41.

  The memory 105 controls the relationship between the DFB part wavelength control current and the reflection spectrum peak wavelength of the first diffraction grating 31, the relation between the DBR part wavelength control current and the reflection spectrum peak wavelength of the second diffraction grating 32a, and the like. A function of storing various setting values controlled by the unit 200 and results monitored by the monitor unit 300 and calculation results of the relationship as initial values is provided. These stored values are used as initial values when the same λ0 is selected next time.

  The monitor unit 300 has a function of monitoring the wavelength and light output of the light oscillated by the wavelength tunable laser 100 and outputting the monitoring result to the control unit 200. Specifically, the monitor unit 300 includes a wavelength monitor unit 201 that monitors the wavelength of light oscillated by the wavelength tunable laser 100, and an optical output monitor unit 202 that monitors the optical output of light oscillated by the wavelength tunable laser 100. It consists of

  The monitor unit 300 may monitor the monitor light L2 output from the light emitting end surface 60b. Or you may monitor the light branched from the laser beam L1 output from the light-projection end surface 60a.

<About the manufacturing method of the wavelength tunable laser 1a>
Next, a method for manufacturing the wavelength tunable laser 1a in the present embodiment will be described.

  FIG. 1 shows an example of the layer structure of the wavelength tunable laser 100 of this embodiment. These layer structures are formed on a semiconductor substrate such as GaAs or InP by OMVPE (Organic Metal Vapor Phase Epitaxy). It can be formed by laminating each layer using a crystal growth method such as a growth) method or a MOCVD (Metal Organic Chemical Vapor Deposition) method. The diffraction grating can be formed using an electron beam exposure apparatus. When the DFB portion 2 and the DBR portion 3 have different layer structures, they can be formed by removing one of the layers by etching and then re-growing another layer structure there.

<About the process flow>
Next, the flow of processing in this embodiment will be described with reference to FIG.

  The light output control unit 104 uses the gain electrode 41 to inject a gain current equal to or greater than the laser oscillation threshold into the gain region 10e in the DFB unit 2 (step S501).

  The DFB part wavelength control unit 101 uses the DFB part wavelength control electrode 45 to adjust the current (DFB part wavelength control current) injected into the diffraction grating formation region 10d in the DFB part 2 to thereby perform the first diffraction. One peak wavelength among the plurality of peak wavelengths of the reflection spectrum in the first optical waveguide 10a on which the grating 31 is formed is controlled to a desired oscillation wavelength λ0 (step S502). At this time, as an initial value, the relationship between the DFB part wavelength control current and the reflection peak wavelength in the first optical waveguide 10 a is measured or calculated in advance and stored in the memory 105.

  The DBR unit wavelength control unit 102 adjusts the current injected into the DBR unit 3 by using the DBR unit wavelength control electrode 43, whereby the reflection spectrum of the second optical waveguide 10b in which the second diffraction grating 32a is formed is adjusted. One peak wavelength among the plurality of peak wavelengths is controlled to λ0 (step S503). At this time, as an initial value, the relationship between the injected current and the reflection peak wavelength in the second optical waveguide 10 b is measured or calculated in advance and stored in the memory 105.

  The optical output monitor unit 202 monitors the optical output of the light oscillated by the wavelength tunable laser 100 (step S504).

  The phase control current control unit 103 controls the light output monitored by the light output monitoring unit 202 to the maximum by adjusting the phase control current using the phase control electrode 42 (step S505).

  The optical output control unit 104 controls the optical output to a desired value by adjusting the gain current injected into the gain region 10e in the DFB unit 2 using the gain electrode 41 (step S506).

  The wavelength monitor unit 201 monitors the wavelength of the light oscillated by the wavelength tunable laser 100 (step S507).

  The DFB unit wavelength control unit 101 uses the DFB unit wavelength control electrode 45 to readjust the DFB unit wavelength control current injected into the diffraction grating formation region 10d in the DFB unit 2, so that the wavelength monitor unit 201 monitors the DFB unit wavelength control unit 101. The wavelength of the light of the tunable laser 100 is controlled to λ0 (step S508).

  The DBR unit wavelength control unit 102 controls the light output of the light oscillated by the wavelength tunable laser 100 to the maximum by readjusting the current injected into the DBR unit 3 using the DBR unit wavelength control electrode 43 (step S509). .

  The phase control current control unit 103 controls the light output of the light oscillated by the wavelength tunable laser 100 to the maximum by adjusting the phase control current injected into the phase shift unit 4 using the phase control electrode 42 ( Step S510).

  The determination unit 106 determines whether the light output of the light oscillated by the wavelength tunable laser 100 monitored by the light output monitor unit 202 is equal to or higher than a desired output (step S511).

  When the optical output of the light oscillated by the wavelength tunable laser 100 monitored by the optical output monitor unit 202 is not equal to or higher than the desired output (“NO” in step S511), the processes in and after step S506 are repeated.

  When the optical output of the light oscillated by the wavelength tunable laser 100 monitored by the optical output monitor unit 202 is equal to or higher than a desired output (“YES” in step S511), the tunable laser 100 monitored by the wavelength monitor unit 201 oscillates. It is determined whether or not the wavelength accuracy at the wavelength of the light is equal to or higher than a desired accuracy (step S512).

  If it is determined that the wavelength accuracy is not higher than the desired accuracy (“NO” in step S512), the processing from step S506 is repeated.

  If it is determined that the wavelength accuracy is equal to or higher than the desired accuracy (“YES” in step S512), the process ends.

  Although not shown in the figure for convenience, when the desired light output wavelength λ 0 is changed, the processing from step S 502 onward is executed.

<About action and effect>
Next, the operation and effect of this embodiment will be described.

  The wavelength tunable laser 100 according to the present invention includes a diffraction grating formation region 10d, which is a region where the first diffraction grating 31 is provided, a gain region 10e that is continuously located in the optical waveguide direction with the diffraction grating formation region 10d, DBR unit 3 including a first optical waveguide 10a including a DFB unit 2 including a second diffraction grating 32a and a second optical waveguide 10b optically coupled to the first optical waveguide 10a. A DFB part wavelength control electrode 45 provided at a position for injecting the DFB part wavelength control current into the diffraction grating forming region 10d in the first optical waveguide 10a of the DFB part 2, and the first optical waveguide 10a of the DFB part 2 A gain electrode 41 provided at a position for injecting a gain current larger than the DFB wavelength control current into the gain region 10e.

  Therefore, the first optical waveguide 10a includes a continuous diffraction grating formation region 10d and a gain region 10e. The first diffraction grating 31 is provided in the diffraction grating formation region 10d, and the gain region 10e that generates gain is included in the gain region 10e that generates gain. Since the first diffraction grating 31 is not provided, the peak wavelength is shifted without changing the peak wavelength interval, and it is possible to obtain an effect that the wavelength control becomes easy.

  Further, the wavelength tunable laser 100 is provided between the DFB unit 2 and the DBR unit 3 and shifts the phase of the light guided through the first optical waveguide 10a and the second optical waveguide 10b. Therefore, it is possible to obtain an effect that laser oscillation is caused by a low threshold current.

  The second diffraction grating 32a forms an SSG. Therefore, since the reflectance is high, it is possible to obtain a larger light output.

  In addition, the wavelength tunable laser device 1a adjusts the DFB wavelength control current to adjust one peak among a plurality of peak wavelengths of the reflection spectrum in the first optical waveguide 10a provided with the first diffraction grating 31. A DFB unit wavelength control unit 101 for controlling the wavelength to a desired value λ 0, and a second optical waveguide provided with a second diffraction grating 32 a by adjusting a DBR unit wavelength control current injected into the DBR unit 3 And a DBR unit wavelength control unit 102 for controlling one peak wavelength of the plurality of peak wavelengths of the reflection spectrum at 10b to λ 0, and more appropriately, the reflection spectrum at the first optical waveguide 10a, the second The reflection spectrum in the optical waveguide 10b can be controlled to a desired value.

  The wavelength tunable laser device 1a includes an optical output monitor unit 202 that monitors the optical output of light oscillated by the wavelength tunable laser 100, and a phase shift unit that maximizes the optical output monitored by the optical output monitor unit 202. 4 is further provided with a phase control current control unit 103 that controls the phase control current injected into 4.

<Second Embodiment>
In the first embodiment, the diffraction grating provided in the second optical waveguide 10b in the DBR portion 3 forms an SSG. However, the diffraction grating provided in the second optical waveguide 10b in the DBR portion 3 may form SG. This will be described below. However, description of parts that are the same as those in the first embodiment will be omitted, and differences will be mainly described.

  FIG. 4 shows a wavelength tunable laser device 1b according to this embodiment. The difference from FIG. 1 is that the second diffraction grating 32b forms SG.

  In this case, the phase shift at each reflection peak of the reflection spectrum in the second optical waveguide 10b provided with the second diffraction grating 32b is caused by the diffraction grating formed in the second optical waveguide 10b having SSG. Since there are few compared with the case where it forms, there exists an advantage which phase control becomes easier.

  Other configurations of the present embodiment are the same as those of the first embodiment.

  The manufacturing method of the wavelength tunable laser 100 of this embodiment is the same as that of the first embodiment. The processing flow in the wavelength tunable laser device 1b of the present embodiment is the same as that of the first embodiment.

  In the wavelength tunable laser 100 according to this embodiment, the second diffraction grating 32b forms an SG, and the phase shift at each reflection peak of the SG is small, so that the phase control can be simplified. .

<Third Embodiment>
In the first embodiment and the second embodiment, the core layer 12 in the first optical waveguide 10a is composed of a single layer. However, the optical waveguide layer 33 and the active layer 34 may have different compositions. This will be described below. However, description of parts that are the same as those in the above embodiment will be omitted, and differences will be mainly described.

  FIG. 5 shows a wavelength tunable laser device 1c according to this embodiment. The difference from FIG. 4 is that the core layer 12 corresponds to a region where the first diffraction grating 31 is not provided and the optical waveguide layer 33 which is a region corresponding to the region where the first diffraction grating 31 is provided. The optical waveguide layer 33 and the active layer 34 have different compositions.

  In the wavelength tunable laser 100 of this embodiment, the band gap energy of the optical waveguide layer 33 (provided with the first diffraction grating 31) of the DFB portion 2 is larger than the band gap energy of the active layer. For this reason, since the light absorption of the optical waveguide 10 can be reduced, the laser threshold can be lowered, and the light output oscillated by the wavelength tunable laser 100 can be increased.

  The optical path length of the DFB unit unit structure, which is the unit structure of the first optical waveguide 10a, is different from the optical path length of the DBR unit unit structure, which is the unit structure of the second optical waveguide 10b. Furthermore, it is desirable that the period of the first diffraction grating 31 and the period of the second diffraction grating 32b are the same.

  In this case, there is an advantage that phase control is simpler because there is little phase shift at each reflection peak of SG.

  Other configurations of the present embodiment are the same as those of the second embodiment.

  The manufacturing method of the wavelength tunable laser 1c of this embodiment is the same as that of the second embodiment. The processing flow in the wavelength tunable laser 1c of this embodiment is the same as that of the second embodiment.

  DESCRIPTION OF SYMBOLS 1a, 1b, 1c ... Variable wavelength laser apparatus, 2 ... DFB part, 3 ... DBR part, 4 ... Phase shift part, 10 ... Optical waveguide, 10a ... 1st optical waveguide, 10b ... 2nd optical waveguide, 10c ... Third optical waveguide, 10d: diffraction grating forming region, 10e: gain region, 11, 13: optical confinement layer, 12: core layer, 21: contact layer, 22: first cladding layer, 23: second cladding layer, 24 ... Semiconductor substrate, 31 ... First diffraction grating, 32a, 32b ... Second diffraction grating, 33 ... Optical waveguide layer, 34 ... Active layer, 41 ... Gain electrode, 42 ... Phase control electrode, 43 ... DBR Part wavelength control electrode, 44 ... n-type electrode, 45 ... DFB part wavelength control electrode, 60a, 60b ... light emitting end face, 100 ... wavelength tunable laser, 200 ... control part, 101 ... DFB part wavelength control part, 102 ... DBR part Wavelength control unit 103... Phase control current control unit 104 ... light output control unit 105 ... memory 106 determination unit 200 ... control unit 201 wavelength monitor unit 202 light output monitor unit 300 monitor unit L1 laser light , L2: Monitor light.

Claims (8)

A DFB portion including a first optical waveguide including a diffraction grating forming region provided with a first diffraction grating, and a gain region located continuously in the optical waveguide direction with the diffraction grating forming region;
A DBR section comprising a second optical waveguide provided with a second diffraction grating and optically coupled to the first optical waveguide;
A DFB part wavelength control electrode provided at a position for injecting a DFB part wavelength control current into the diffraction grating formation region in the first optical waveguide of the DFB part;
A gain electrode provided at a position for injecting a gain current larger than the DFB wavelength control current into the gain region in the first optical waveguide of the DFB portion;
A tunable laser comprising:   2. The phase shift unit according to claim 1, further comprising a phase shift unit provided between the DFB unit and the DBR unit and configured to shift a phase of light guided through the first optical waveguide and the second optical waveguide. Tunable laser.   The wavelength tunable laser according to claim 1, wherein the second diffraction grating forms an SG.   The wavelength tunable laser according to claim 1, wherein the second diffraction grating forms an SSG. The wavelength tunable laser according to any one of claims 1 to 4,
A DFB unit that controls one peak wavelength among a plurality of peak wavelengths of a reflection spectrum in the first optical waveguide provided with the first diffraction grating to a predetermined value by adjusting the wavelength control current of the DFB unit. A wavelength control unit;
By adjusting the DBR part wavelength control current injected into the DBR part, one peak wavelength among the plurality of peak wavelengths of the reflection spectrum in the second optical waveguide provided with the second diffraction grating is changed to the peak wavelength. A DBR wavelength control unit for controlling to a predetermined value;
A tunable laser device comprising: An optical output monitor for monitoring the optical output of the light oscillated by the wavelength tunable laser;
A phase control current control unit for controlling a phase control current to be injected into the phase shift unit so that the light output monitored by the light output monitor unit is maximized;
The wavelength tunable laser device according to claim 5, further comprising: In the 1st optical waveguide in which the 1st diffraction grating of the tunable laser was provided by adjusting the DFB part wavelength control current in the tunable laser according to any one of claims 1 to 4 A DFB unit wavelength control step for controlling one peak wavelength of the plurality of peak wavelengths of the reflection spectrum to a predetermined value;
By adjusting the wavelength control current of the DBR section in the wavelength tunable laser, one peak among a plurality of peak wavelengths of the reflection spectrum in the second optical waveguide provided with the second diffraction grating of the wavelength tunable laser DBR unit wavelength control step for controlling the wavelength to the predetermined value;
A tunable laser control method comprising: A light output monitoring step for monitoring the light output of the light oscillated by the wavelength tunable laser;
Phase control provided between the DFB unit and the DBR unit of the wavelength tunable laser and shifted to the phase shift unit for shifting the phase of the light so that the optical output monitored in the optical output monitoring step is maximized. A phase control current control step for controlling the current for use;
The wavelength tunable laser control method according to claim 7, further comprising:

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